US20070105715A1 - Particulate matter oxidation catalyst and filter - Google Patents

Particulate matter oxidation catalyst and filter Download PDF

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US20070105715A1
US20070105715A1 US10/560,899 US56089905A US2007105715A1 US 20070105715 A1 US20070105715 A1 US 20070105715A1 US 56089905 A US56089905 A US 56089905A US 2007105715 A1 US2007105715 A1 US 2007105715A1
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particulate matter
diesel engine
engine exhaust
exhaust gas
perovskite
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Hisashi Suda
Takuya Yano
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Dowa Electronics Materials Co Ltd
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Dowa Holdings Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/944—Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/32—Manganese, technetium or rhenium
    • B01J23/34—Manganese
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/78—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with alkali- or alkaline earth metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/83—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2279/00—Filters adapted for separating dispersed particles from gases or vapours specially modified for specific uses
    • B01D2279/30—Filters adapted for separating dispersed particles from gases or vapours specially modified for specific uses for treatment of exhaust gases from IC Engines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts

Definitions

  • This invention relates to a catalyst used for the combustion of particulate matter (PM) contained in the exhaust gas of diesel engines, and to a particulate matter filter for control of diesel engine exhaust emissions using this catalyst.
  • PM particulate matter
  • Nitrogen oxides (NO x ) and particulate matter (PM) are particular problems with respect to diesel engine exhaust.
  • the particulate matter comprises fine particles constituted primarily of carbon, and the most typical method of their removal has been a method whereby a diesel particulate filter (DPF) is placed in the exhaust line to trap the particulate matter.
  • DPF diesel particulate filter
  • This filter regeneration process may be performed by a method wherein an electric heater, burner or the like is used to burn the particulate matter, or a method wherein the particulate filter carries a catalyst, and its catalytic effect lowers the ignition temperature of the particulate matter, thereby continuously burning the particulate matter at the exhaust gas temperature.
  • the former method requires the addition of outside energy and the system becomes complex, so the latter catalytic method is considered to be preferable.
  • Examples of this catalytic method include those disclosed in Patent Reference Documents 1 and 2 and Non-Patent Reference Documents 1 and 2, where platinum (Pt) is used as the catalyst metal.
  • platinum Pt
  • a way of solving the problem of increased costs due to the use of noble metals as the catalyst is an important problem.
  • Patent Reference Document 3 recites the use of a perovskite-type composite oxide in a DPF, and indicates that the carbon black ignition temperature is decreased by the use thereof.
  • Non-Patent Reference Document 3 proposes the use of V 2 O 5 , MoO 3 , PbO, Cs 2 MoO 4 , AgVO 3 or eutectic mixtures thereof as melt moving type catalysts. These mixtures melt at exhaust gas temperatures, move over the surface of a honeycomb substrate, come into contact with particulate matter and oxidize and burn it. Thus, the lower the melting point and higher the mobility of the mixtures, the greater the effect of burning particulate matter at low temperature becomes, so these are said to be more superior as catalysts.
  • low-melting point substances are highly volatile, so they have a problem in that their durability is low. Consequently, they have yet to find practical application.
  • Non-Patent Reference Document 4 proposes the use of a perovskite-type composite oxide containing potassium (K).
  • K potassium
  • Patent Reference Document 1 JP Hei 11-253757 A
  • Patent Reference Document 2 JP 2003-222014 A
  • Patent Reference Document 3 JP Hei 06-29542 B
  • Non-Patent Reference Document 1 Earozoru Kenky u [“Aerosol Research,” published by the Japan Association of Aerosol Science and Technology] (2003), Vol. 18, No. 3, pp. 185-194
  • Non-Patent Reference Document 2 Jid o sha Gijutsu Kai Gakujutsu K o enkai Maezurish u [“Proceedings of the Annual Congress of the Society of Automotive Engineers of Japan”] (2002), Vol. 22, No. 02, pp. 5-8
  • Non-Patent Reference Document 3 Kinzoku [“Metal” magazine] Vol. 74 (2004), No. 5, pp. 449-453
  • Non-Patent Reference Document 4 Nippon Seramikkusu Ky o kai Gakujutsu Ronbunshi (Journal of the Ceramic Society of Japan) (2003), Vol. 111, No. 129, pp. 852-856
  • An object of the present invention is to provide a highly active and highly durable catalyst able to burn the particulate matter (PM) in diesel engine exhaust at low temperature.
  • the catalyst does not contain noble metals and is thus inexpensive, and also its constituent materials are not volatized at exhaust gas temperatures, so it has superior durability.
  • Another object is to provide a diesel particulate filter (DPF) for control of diesel engine exhaust emissions that uses the catalyst.
  • DPF diesel particulate filter
  • This perovskite-type composite oxide may be represented by the structural formula RTO 3 , wherein R is one or more elements selected from a group made up of the rare-earth elements, alkali metal elements excluding Na and alkaline-earth metal elements; and T is one or more elements selected from a group made up of the transition metal elements and Mg, Al and Si.
  • a preferable constitution is one wherein R comprises one or more elements selected from a group made up of La, Sr, Ba, Ca and Li, and T comprises one or more elements selected from a group made up of Mn, Fe, Co, Cu, Zn, Ga, Zr, Mo, Mg, Al and Si.
  • Y is treated as a rare-earth element.
  • this catalyst initiates the combustion of particulate matter constituted primarily of carbon in diesel engine exhaust at a temperature below 450° C.
  • the present invention also provides a particulate matter filter for control of diesel engine exhaust emissions that carries any of these catalysts.
  • a diesel engine exhaust particulate matter (PM) oxidation catalyst that uses the perovskite-type composite oxide defined in the present invention is able to burn particulate matter that accumulates in a diesel particulate filter (DPF) for control of diesel engine exhaust emissions at low temperature, so the amount of particulate matter released into the atmosphere is reduced and also the temperature of the exhaust gas passing through the filter can be lowered in comparison with that in the prior art, and thus the load on various members of the exhaust system is lessened.
  • catalytic action with high activity can be achieved without containing noble metals, so the materials cost for the particulate filter can be reduced.
  • the catalyst according to the present invention does not contain material that is volatilized at exhaust gas temperatures, so it also has superior durability. Accordingly, the present invention improves the durability of a DPF system and provides a greatly reduced total cost.
  • FIG. 1 is a diagram showing the x-ray diffraction pattern of a perovskite-type composite oxide used in Working Example 1.
  • FIG. 2 is a graph of the changes in the NO concentration and CO 2 concentration in the output-side gas as a function of temperature in the warm-up process when simulated diesel engine exhaust is passed through a sample of particles of the perovskite-type composite oxide according to Working Example 1.
  • FIG. 3 is a graph of the change in the CO 2 concentration in the output-side gas as a function of temperature in the warm-up process when simulated diesel engine exhaust is passed through samples of honeycomb filters carrying catalysts obtained by means of Working Examples 1 and 2 and Comparative Example 1.
  • FIG. 4 is a graph of the change in the CO 2 concentration in the output-side gas as a function of temperature in the warm-up process when simulated diesel engine exhaust is passed through samples of honeycomb filters carrying catalysts obtained by means of Working Examples 2 and 3 and Comparative Example 1.
  • the nitrogen mono-oxide (NO) contained in diesel engine exhaust is oxidized on the surface of a metal catalyst such as Pt to form nitrogen dioxide (NO 2 ), and this NO 2 is used to oxidize (burn) particulate matter constituted primarily of carbon, thereby regenerating the filter.
  • a metal catalyst such as Pt
  • NO 2 nitrogen dioxide
  • a perovskite-type composite oxide that has an NO adsorption domain at a temperature range below 450° C. (e.g., 200-450° C.) is used instead of the metal catalyst such as Pt.
  • this type of perovskite-type composite oxide was found to have the property of simultaneously inducing the reaction of oxidizing (burning) carbon particles to CO 2 and re-releasing NO at around 300-450° C.
  • the particulate matter (PM) constituted primarily of carbon contained in diesel engine gas normally has a combustion temperature of 500° C. or higher, so the perovskite-type composite oxide used in the present invention has the catalytic action of burning PM at low temperature.
  • This perovskite-type composite oxide may be represented by the generic formula RTO 3 .
  • R is one or more elements selected from a group made up of the rare-earth elements (Y is also treated as a rare-earth element), alkali metal elements excluding Na and alkaline-earth metal elements. However, it preferably contains at least one or more alkali metal elements and alkaline-earth metal elements. The above catalytic action is exhibited particularly markedly by such compositions.
  • T is one or more elements selected from a group made up of the transition metal elements plus Mg, Al and Si. While there are no particular limitations on the rare-earth elements comprising R, they may be Y, La, Ce, Nd, Sm, Pr or the like, or preferably La.
  • transition-metal elements constituting T may be Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Zr, Mo, Ru, Rh, Pd, Ag, In, Sn, Pt, Au or the like, or preferably Ti, Mn, Fe, Co, Ni, Cu, Zn, Ga, Zr or Mo.
  • elements other than the rare-earth elements that may constitute R include alkali metal elements excluding Na and alkaline-earth metal elements that may be contained in a form replacing a portion of the rare-earth elements. Examples include Li, K, Ca, Sr, Ba and the like, but these are preferably Li, Sr or Ba. From a standpoint of achieving a marked catalytic effect, rather than having R comprise only rare-earth elements, it is more preferable for it to include at least one or more of Li, Ca, Sr or Ba.
  • Patent Reference Document 3 discloses the use of a Na-based precipitating agent in order to obtain a precipitate of the composite oxide, but according to the research conducted by the present inventors, it is necessary for effecting the catalytic action for burning PM at low temperature to make the amount of Na within the perovskite-type composite oxide as small as possible, or specifically the Na content should be 0.7 mass % or less, or more preferably zero. It is typically difficult to remove Na-based constituents that are incorporated from the raw materials. It was found that if Na-based constituents are present as impurities, the ignition temperature tends to increase as shown in the subsequent Working Examples.
  • the perovskite-type composite oxide having such a composition what has an NO adsorption domain within the temperature range 200-450° C., and has the property of simultaneously inducing the reaction of oxidizing (burning) carbon particles to CO 2 and re-releasing NO at around 300-450° C. are realized. If a powder of such a perovskite-type composite oxide is carried upon a cordierite or SiC or other substrate constituting a honeycomb instead of the conventional Pt catalyst or the like, then one obtains a highly active and highly durable diesel particulate filter (DPF) for purification of diesel engine exhaust emissions that is able to burn the particulate matter (PM) in diesel engine exhaust at low temperature.
  • DPF diesel particulate filter
  • the perovskite-type composite oxide used in the present invention may be produced by a coprecipitation method, organic complex method, alkoxide method, or a method using an amorphous precursor, for example.
  • a coprecipitation method organic complex method
  • alkoxide method or a method using an amorphous precursor, for example.
  • an aqueous solution of salts of raw materials that contains salts of the aforementioned elements in stoichiometric ratios appropriate to produce the perovskite-type composite oxide RTO 3 is prepared, this aqueous solution is mixed with a neutralizing agent to induce coprecipitation and then the coprecipitate thus obtained is dried and then heat-treated.
  • the salts of the elements used are not particularly limited, but rather any of their sulfates, nitrates, phosphates, chlorides or other inorganic salts, acetates, oxalates or other organic salts or the like may be used. Among these, the acetates and nitrates are particularly suitable.
  • the aqueous solution of salts of raw materials may be prepared by adding the salts of the aforementioned elements to water so as to reach the desired stoichiometric ratios and then stirring.
  • this aqueous solution of salts of raw materials is mixed with a neutralizing agent to induce coprecipitation.
  • a neutralizing agent there is no particular limitation with respect to the neutralizing agent used, but rather ammonia, potassium hydroxide and other inorganic bases, or triethylamine, pyridine or other organic bases can be used.
  • the neutralizing agent is mixed in until the pH of the slurry formed after adding the neutralizing agent becomes 6-14. When mixed in this manner, a highly crystalline coprecipitate of hydroxides of the various elements can be obtained.
  • the use of a base that contains Na at this time is not preferable because Na will become incorporated into the product.
  • the coprecipitate thus obtained is rinsed with water and may be dried by vacuum drying or forced-air drying, for example, and then subjected to heat treatment at 600-1200° C., or preferably 800-1000° C. to obtain the desired perovskite-type composite oxide.
  • heat treatment at 600-1200° C., or preferably 800-1000° C.
  • the atmosphere used at the time of heat treatment is no particular limitation on the atmosphere used at the time of heat treatment as long as it is within a range wherein the perovskite-type composite oxide is produced, and an air, nitrogen, argon or hydrogen atmosphere or one of these combined with water vapor, or preferably an air or nitrogen atmosphere or one of these combined with water vapor may be used.
  • a salt that forms an organic complex of citric acid, malic acid or the like and salts of the aforementioned elements may be added to water in the desired stoichiometric ratios and stirred to prepare an aqueous solution of salts of raw materials.
  • This aqueous solution of salts of raw materials is dried to form an organic complex of the aforementioned elements and then calcined and subjected to heat treatment to obtain the perovskite-type composite oxide.
  • the salts of the elements used may be the same as those used in the case of the coprecipitation method.
  • the aqueous solution of salts of raw materials may also be prepared by dissolving a mixture of the raw material salts of the various elements in the desired stoichiometric ratios and then mixing this with an aqueous solution of a salt that forms an organic complex.
  • the molar ratio of the salt that forms an organic complex that is mixed in the blend is preferably around 1.2-3 mol per 1 mol of the perovskite-type composite oxide thus obtained.
  • this raw-material liquid is dried to obtain the aforementioned organic complex.
  • drying conditions used as long as the temperature is such that the organic complex does not decompose so for example, drying can be performed at room temperature to roughly 150° C., or preferably from room temperature to 110° C. to quickly remove the moisture.
  • the aforementioned organic complex is thus obtained.
  • the organic complex thus obtained is calcined and then heat-treated. Calcining may be performed by heating to 250° C. or higher in a vacuum or in an inert gas atmosphere, for example. Thereafter, heat treatment at 600-1000° C., or preferably 600-950° C., for example may be performed to obtain the desired perovskite-type composite oxide. At this time, there is no particular limitation on the atmosphere used at the time of heat treatment as long as it is within a range wherein the perovskite-type composite oxide is produced, and an air, nitrogen, argon or hydrogen atmosphere or one of these combined with water vapor, or preferably an air or nitrogen atmosphere or one of these combined with water vapor may be used.
  • an alkoxide solution of raw materials that contains alkoxides of the aforementioned elements in stoichiometric ratios is prepared, this solution of raw materials is reacted with water to induce hydrolysis and obtain a precipitate.
  • the precipitate thus obtained can be dried and then heat-treated to obtain the desired perovskite-type composite oxide.
  • the alkoxides of the elements used are not particularly limited as long as the elements mix uniformly, but rather for example, any alcoholates formed of methoxy, ethoxy, propoxy, isopropoxy, butoxy and other alkoxy groups may be used.
  • the alkoxide solution of raw materials may be prepared by dissolving these alkoxides in an organic solvent so as to reach the desired stoichiometric ratios and then stirring and blending.
  • the organic solvent that can be used is not particularly limited as long as it is able to dissolve the alkoxides of the elements, so for example, benzene, toluene, xylene and the like may be used.
  • the precipitate thus obtained is rinsed with water and may be dried by vacuum drying or forced-air drying, for example, and then subjected to heat treatment at 500-1000° C., or preferably 500-850° C. to obtain the desired perovskite-type composite oxide.
  • the atmosphere used at the time of heat treatment is no particular limitation on the atmosphere used at the time of heat treatment as long as it is within a range wherein the perovskite-type composite oxide is produced, and an air, nitrogen, argon or hydrogen atmosphere or one of these combined with water vapor, or preferably an air or nitrogen atmosphere or one of these combined with water vapor may be used.
  • a precursor substance comprising of a powdery amorphous containing the aforementioned elements in stoichiometric ratios appropriate to produce the perovskite-type composite oxide with the RTO 3 structure may be heat treated at low temperature to obtain the perovskite-type composite oxide.
  • Such an amorphous precursor can be obtained by preparing an aqueous solution of salts of raw materials that contains salts of the aforementioned elements in stoichiometric ratios appropriate to produce the perovskite-type composite oxide with the RTO 3 structure, reacting this aqueous solution with a precipitating agent which is a carbonate containing ammonium ion or an alkaline carbonate at a reaction temperature of 60° C. or lower and at a pH of 6 or higher to make a precipitation product, and drying its filtrate.
  • a precipitating agent which is a carbonate containing ammonium ion or an alkaline carbonate
  • a nitrate, sulfate, chloride or other aqueous mineral salt of R and a nitrate, sulfate, chloride or other aqueous mineral salt of T are dissolved in water to prepare an aqueous solution wherein the molar ratio of the R element to the T element becomes 1:1.
  • the molar ratio of the R element to the T element should ideally be made 1:1, but even if it is not 1:1 a perovskite-type composite oxide can still be formed. Accordingly, even if the molar ratio of the R element to the T element is shifted somewhat from 1:1, it is fine as long as it is a value that allows a perovskite-type composite oxide to be formed.
  • the R element may comprise two or more components and the T element may also comprise two or more components.
  • the various components should be dissolved such that the molar ratio of the total number of moles of the elements that constitute R to the total number of moles of the elements that constitute T becomes roughly 1:1.
  • the ion concentrations of R and T in the solution in which the precipitate is to be formed are such that the upper limit is determined by the solubility of the salts used and should be such that crystalline compounds of R or T do not precipitate, but normally the total ion concentration of R and T is preferably roughly in the range 0.01-0.60 mol/L.
  • a precipitating agent which is a carbonate containing ammonium ion or an alkaline carbonate
  • examples of such a precipitating agent include ammonium carbonate, ammonium hydrogen carbonate and the like, but if necessary, aqua ammonia or another base may also be added.
  • aqua ammonia or another base may also be added.
  • carbon dioxide after a precipitate is formed using aqua ammonia or the like, it is also possible to blow in carbon dioxide to obtain an amorphous substance suitable as the amorphous precursor to the perovskite-type composite oxide used in the present invention.
  • the pH of the solution be controlled to be in the range 6-11.
  • the reaction temperature can be 60° C. or lower. If the reaction is started at a temperature above 60° C., crystalline compound particles of R or T may be produced, and these may interfere with the conversion to an amorphous precursor and are thus not preferable.
  • the use of a precipitating agent that contains sodium was found to increase the ignition temperature. This is thought to be because, if sodium is incorporated into the precursor, no matter how well it is washed, it will still remain at a concentration of roughly several hundred ppm and this will cause deleterious effects on the characteristics of ignition temperature and the like.
  • the amorphous precursor thus obtained is rinsed with water as optionally and may be dried by vacuum drying or forced-air drying, for example, and then subjected to heat treatment at 500-1000° C., or preferably 500-800° C. to obtain the desired perovskite-type composite oxide.
  • heat treatment at 500-1000° C., or preferably 500-800° C.
  • the atmosphere used at the time of heat treatment is no particular limitation on the atmosphere used at the time of heat treatment as long as it is within a range wherein the perovskite-type composite oxide is produced, and an air, nitrogen, argon or hydrogen atmosphere or one of these combined with water vapor, or preferably an air or nitrogen atmosphere or one of these combined with water vapor may be used.
  • the precipitate thus obtained was recovered by filtration, rinsed with water and dried at 110° C.
  • the powder thus obtained is called the precursor powder.
  • FIG. 1 shows the x-ray diffraction pattern of the calcine thus obtained.
  • this calcine was confirmed to be a substance with a (La 0.8 Sr 0.2 )MnO 3 perovskite-type composite oxide phase.
  • the calcine was confirmed to have a (La 0.8 Sr 0.2 )FeO 3 perovskite-type composite oxide phase.
  • Na exhibited a value less than 1 ppm (less than the measurement limit).
  • a portion of the perovskite-type composite oxide obtained in Working Example 2 was sampled and subjected to heat treatment for 24 hours at 800° C. The heat treatment was performed in air.
  • SiO 2 (Wakogel C-100 made by Wako Pure Chemical Industries, Ltd.) was impregnated with Pt using an aqueous solution of [Pt(NH 3 ) 4 ](OH) 2 and dried by forced air for 12 hours at 120° C. The impregnate thus obtained was reduced for 4 hours at 400° C. in 4% H 2 (the remainder being N 2 ) and then subsequently oxidized for 2 hours at 500° C. in air to obtain SiO 2 containing Pt. The Pt content of the SiO 2 was 1 mass % at this time.
  • the PM combustion temperature was evaluated as follows in accordance with the method recited in Kanky o Hozen Kenky u Seikash u (“Environmental Protection Research Results,” National Institute of Industrial Health of Japan) (1999), 1, pp. 37-1-37-13.
  • Each of the powders obtained in Working Example 1 and Comparative Example 1 was press-formed with a die press at 500 kg/cm 2 and then crushed to prepare particulate samples with a grain size of 0.25-0.50 mm.
  • As simulated PM commercial carbon black was added to these particulate samples so as to become 1 mass. %, and they were mixed by shaking in a glass bottle. The state of contact between the carbon and the catalyst samples achieved by this mixing method becomes the state of “loose contact” close to that when PM is actually caught on a filter.
  • the aforementioned particulate samples mixed with carbon black were loaded into ventilated fixed beds which were put into contact with a constant flow of the simulated diesel engine exhaust gas shown in Table 1, so that the concentrations of CO 2 and NO in the gas passing through the ventilated fixed beds could be continuously measured. Then, once the flow of simulated diesel exhaust gas was started, the temperature was raised from room temperature to 800° C. at a warm-up rate of 10° C./minute while the concentrations of CO 2 and NO in the gas passing through the ventilated fixed beds was monitored.
  • the CO 2 concentration and the NO concentration were measured using a Nicolet Nexus 470 FT-IR.
  • FIG. 2 illustrates an example of the changes in the CO 2 concentration and NO concentration in the case of Working Example 1.
  • the downstream NO concentration dropped rapidly at 200-250° C. and exhibited values below 200 ppm over approximately the range 250-350° C. This means that the NO drawn into the air flow began to be adsorbed to the perovskite-type composite oxide at 200-250° C. Thereafter, as the CO 2 concentration increased rapidly from around 350° C., the NO concentration began to increase again. Then, from around 400° C., the NO concentration began to exhibit a value nearly equal to the inflow concentration of 500 ppm. Because the increase in the NO concentration from around 350° C.
  • the NO adsorbed to the perovskite-type composite oxide was active in the combustion of carbon black. It is thought that when the NO adsorbed to the perovskite-type composite oxide is desorbed, some substance that has a strong oxidation activity (e.g., activated oxygen) is released, thus causing the combustion (oxidation) of carbon black.
  • the ignition temperature of the carbon black used here is around 560° C., so one can see that the perovskite-type composite oxide acted as a catalyst in inducing low-temperature combustion of the simulated PM.
  • the ignition temperature T 10 was found in the measure as the temperature at which the amount of CO 2 generated as found by measuring the gas passing through the ventilated fixed bed reached 10% of the total amount of CO 2 generated.
  • the results in Working Example 1 and Comparative Example 1 are presented in Table 2. TABLE 1 NO O 2 H 2 O N 2 500 ppm 10% 7% Remainder
  • the perovskite-type composite oxide according to Working Example 1 demonstrated a lower PM combustion temperature and higher activity than the Pt-impregnated SiO 2 catalyst according to Comparative Example 1.
  • this perovskite-type composite oxide contains no water-soluble components such as potassium (K), so it can be expected to exhibit good durability.
  • PM can be burned at low temperature using the perovskite-type composite oxide that adsorbs NO in the 200-450° C. temperature range, and thus the amount of PM released can be reduced.
  • the mechanism by which this low-temperature combustion of PM occurs is unclear at the present time, but the following can be surmised.
  • NO within the exhaust gas is oxidized by O 2 in the atmosphere by means of catalytic action of the perovskite-type composite oxide, thus being adsorbed to the perovskite-type composite oxide in the form of NO 2 or nitrate ion.
  • the PM is caused to combust at low temperature by the nitrogen oxide or activated oxygen thus formed, thereby producing NO and CO 2 .
  • Each of the powders obtained in Working Example 1, Working Example 2 and Comparative Example 1 was wash-coated onto a 200 cpsi cordierite honeycomb structure used as a DPF.
  • the amount of coating was such that there were 10 parts by mass powder to 100 parts by mass honeycomb structure. Thereafter, they were uniformly covered with commercial carbon black as simulated PM.
  • the amount of carbon applied was such that there were 2 parts by mass powder to 100 parts by mass honeycomb structure.
  • honeycomb filter samples thus obtained were loaded into ventilated fixed beds which were put into contact with a constant flow of the simulated diesel engine exhaust gas shown in Table 3, so that the concentrations of CO 2 in the gas passing through the ventilated fixed beds could be continuously measured.
  • the temperature was raised from room temperature to 750° C. at a warm-up rate of 10° C./minute while the CO 2 concentration in the gas passing through the ventilated fixed beds was monitored.
  • the CO 2 concentration was measured using a Shimadzu FID-methanizer.
  • FIG. 3 illustrates an example of the changes in the CO 2 concentration in Working Examples 1 and 2 and Comparative Example 1.
  • the increase in the CO 2 concentration accompanying carbon black (simulated PM) combustion in Working Examples 1 and 2 occurred starting at a low temperature of approximately 300° C.
  • the perovskite-type composite oxide acted as a catalyst in inducing low-temperature combustion of the simulated PM.
  • the ignition temperature T 10 is presented in Table 4. TABLE 3 NO O 2 H 2 O N 2 SV 1000 ppm 10% 7% Remainder 20000/h
  • the perovskite-type composite oxide catalysts according to the present invention (Working Examples 1 and 2) were confirmed to exhibit the action of markedly lowering the PM combustion temperature, and were found to have a high practical value.
  • the catalyst according to the present invention can be expected to give higher performance and higher reliability than the conventional precious-metal catalysts in practice.
  • FIG. 4 also illustrates the results with a Pt catalyst that was not heat-treated (that of Comparative Example 1) and a perovskite-type composite oxide that was not subjected to heat treatment (that of Working Example 2), for comparison with that of Working Example 3.
  • the oxide of Working Example 3 that was subjected to heat treatment exhibited a somewhat lower efficiency of conversion from carbon to CO 2 in the low-temperature region, but no extreme drop in activity occurred.
  • that of Working Example 3 that was subjected to heat treatment kept activity superior to that of the conventional Pt catalyst according to Comparative Example 1 that underwent catalytic evaluation without being subjected to heat treatment.
  • the perovskite-type composite oxide according to the present invention keeps its catalytic activity even under severe environments and is able to perform the combustion of particulate matter in an environment at a lower temperature in comparison to conventional catalysts.

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US20100086458A1 (en) * 2008-10-03 2010-04-08 Gm Global Technology Operations, Inc. Method and architecture for oxidizing nitric oxide in exhaust gas from hydrocarbon fuel source with a fuel lean combustion mixture
US20100229533A1 (en) * 2009-03-16 2010-09-16 Gm Global Technology Operations, Inc. PEROVSKITE-TYPE COMPOUNDS FOR USE IN LEAN NOx TRAPS
US20110070139A1 (en) * 2008-10-03 2011-03-24 Gm Global Technology Operations, Inc. Catalyst combinations and methods and systems for oxidizing nitric oxide in a gas stream
US20120159927A1 (en) * 2010-12-22 2012-06-28 GM Global Technology Operations LLC Perovskite oxide compounds for use in exhaust aftertreatment systems
US20130252808A1 (en) * 2012-03-23 2013-09-26 Yoshihiro Yamazaki Catalysts for thermochemical fuel production and method of producing fuel using thermochemical fuel production
WO2014049445A3 (fr) * 2012-09-28 2014-05-15 Aditya Birla Science And Technology Company Limited Procédés et compositions pour désulfurer des compositions
US8943811B2 (en) 2010-12-22 2015-02-03 GM Global Technology Operations LLC Perovskite-based catalysts, catalyst combinations and methods of making and using the same
DE102012000280B4 (de) * 2011-01-13 2016-08-04 GM Global Technology Operations LLC (n. d. Ges. d. Staates Delaware) Verfahren zur Begünstigung der Oxidation von NO zu NO2 in einem Abgasstrom eines im Betrieb befindlichen Dieselmo-tors.
US9410042B2 (en) 2012-03-30 2016-08-09 Aditya Birla Science And Technology Company Ltd. Process for obtaining carbon black powder with reduced sulfur content
US9828895B2 (en) 2015-09-30 2017-11-28 Hyundai Motor Company Exhaust gas post-processing system
US9873797B2 (en) 2011-10-24 2018-01-23 Aditya Birla Nuvo Limited Process for the production of carbon black
CN114870848A (zh) * 2022-03-24 2022-08-09 桂林理工大学 一种可降低柴油发动机碳烟氧化温度的管状钙钛矿型复合氧化物催化剂

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US8268274B2 (en) 2008-10-03 2012-09-18 GM Global Technology Operations LLC Catalyst combinations and methods and systems for oxidizing nitric oxide in a gas stream
US20110070139A1 (en) * 2008-10-03 2011-03-24 Gm Global Technology Operations, Inc. Catalyst combinations and methods and systems for oxidizing nitric oxide in a gas stream
US7964167B2 (en) * 2008-10-03 2011-06-21 GM Global Technology Operations LLC Method and architecture for oxidizing nitric oxide in exhaust gas from hydrocarbon fuel source with a fuel lean combustion mixture
US20100086458A1 (en) * 2008-10-03 2010-04-08 Gm Global Technology Operations, Inc. Method and architecture for oxidizing nitric oxide in exhaust gas from hydrocarbon fuel source with a fuel lean combustion mixture
US20100229533A1 (en) * 2009-03-16 2010-09-16 Gm Global Technology Operations, Inc. PEROVSKITE-TYPE COMPOUNDS FOR USE IN LEAN NOx TRAPS
US8513155B2 (en) * 2009-03-16 2013-08-20 GM Global Technology Operations LLC Perovskite-type compounds for use in lean NOx traps
US8943811B2 (en) 2010-12-22 2015-02-03 GM Global Technology Operations LLC Perovskite-based catalysts, catalyst combinations and methods of making and using the same
US9732687B2 (en) * 2010-12-22 2017-08-15 GM Global Technology Operations LLC Perovskite oxide compounds for use in exhaust aftertreatment systems
DE102011121222B4 (de) 2010-12-22 2021-12-30 GM Global Technology Operations LLC (n. d. Ges. d. Staates Delaware) Produkt umfassend einen Partikelfilter, der einen Perowskit-Katalysator und ein NOx-Speichermaterial umfasst, und Verwendung desselben
CN102536396A (zh) * 2010-12-22 2012-07-04 通用汽车环球科技运作有限责任公司 用于废气后处理系统中的钙钛矿氧化物化合物
US20120159927A1 (en) * 2010-12-22 2012-06-28 GM Global Technology Operations LLC Perovskite oxide compounds for use in exhaust aftertreatment systems
DE102012000280B4 (de) * 2011-01-13 2016-08-04 GM Global Technology Operations LLC (n. d. Ges. d. Staates Delaware) Verfahren zur Begünstigung der Oxidation von NO zu NO2 in einem Abgasstrom eines im Betrieb befindlichen Dieselmo-tors.
US9873797B2 (en) 2011-10-24 2018-01-23 Aditya Birla Nuvo Limited Process for the production of carbon black
US9873109B2 (en) 2012-03-23 2018-01-23 California Institute Of Technology Catalysts for thermochemical fuel production and method of producing fuel using thermochemical fuel production
US20130252808A1 (en) * 2012-03-23 2013-09-26 Yoshihiro Yamazaki Catalysts for thermochemical fuel production and method of producing fuel using thermochemical fuel production
US9410042B2 (en) 2012-03-30 2016-08-09 Aditya Birla Science And Technology Company Ltd. Process for obtaining carbon black powder with reduced sulfur content
WO2014049445A3 (fr) * 2012-09-28 2014-05-15 Aditya Birla Science And Technology Company Limited Procédés et compositions pour désulfurer des compositions
RU2641101C2 (ru) * 2012-09-28 2018-01-16 Адития Бирла Сайенс Энд Текнолоджи Компани Лимитед Способы и состав для десульфурации составов
US9828895B2 (en) 2015-09-30 2017-11-28 Hyundai Motor Company Exhaust gas post-processing system
CN114870848A (zh) * 2022-03-24 2022-08-09 桂林理工大学 一种可降低柴油发动机碳烟氧化温度的管状钙钛矿型复合氧化物催化剂

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